Hi all, I started with a simple problem: one of the old lead-acid batteries on our MkI finally died this year. The last evidence of a power plan update (other than new batteries) that I can deduce was pre-2001'ish with a poorly executed gummy-plug and amp meter edit.
My initial plan was conservative: replace it with an AGM or TPPL battery and repurpose my existing oversized lead-acid “start” battery as part of the house bank. Correct/update wiring as required. Then I realized AGM/TPPL pricing was close to (or the same as) many LiFePO4/LFP options… and now I’m deep in the rabbit hole looking at an inverter/charger setup (ex: Victron MultiPlus-II 12/3000/120-50), plus the other supporting bits and wholesale rewiring.
Before I buy anything, I’d love to learn from people who have already installed these:
- Where did you mount your inverter/charger? (nav station, under settee, aft berth, near batteries, locker, etc.) Photos would be awesome.
- Why that location? (DC cable length to batteries, AC wiring to panel, ventilation/heat, noise, dry/corrosion-safe, service access)
- Any Catalina 36 Mk1-1.5 “gotchas”? Clearance, mounting structure, access to fuses/switches, routing heavy DC cables, etc. Universal truths (a.k.a Dohs!) are welcome too.
- If you did it again today in 2026, what would you do differently? (different location, smaller/larger unit, separate inverter + charger, different battery placement, more ventilation/access, etc.)
Not looking to start a brand debate, mainly trying to avoid mounting a heavy, potentially loud unit somewhere I’ll regret later.
Thanks!
J. W. Bell
S/V <currently unnamed>
1985 MkI TR #462 M25
MKE, WI
s/v Brazen Article is a MKII (2001, #1925) so the layout may be different. I mounted the Victron Multiplus under the nav station desk. That is close to the electric panel and battery compartment. Wiring was pretty easy once I drilled a few holes and routed cable. No problem with ventilation or excessive noise.
I have two 300 Amp LifePo4 batteries and an AGM start battery in the battery compartment on the other side of the wall.
Most of the time I'm traveling, at anchor or on a mooring. Charging is from solar panels (1200 watts) or DC to DC chargers running off the alternator. With several cloudy days I can fire up a 2000 inverter generator (Yamaha - similar to the Honda) plugged into the stern power input.
I use a lot of electricity - Kuerig coffee, air fryer, toaster, Starlink, television and computers but I haven't had any issues, no reason to change anything so far.
Denis
Brazen Article #1925
2001 Catalina 36 MKII
Like you, I have 1985 Mk 1. My inverter/charger, a Magnum ME-2012, is a 2000W/100A unit and it mounted to the hull outboard of the seat directly in front of the Nav. Station. The PO and, later me improved on glassing the mounts to hull. I have 3 battery banks: two 250 Amp-Hr sets of two 125 Amp-Hr Lifeline GPL-31XTs. One set is under the seat in front of the Nav. Station along with one Lifeline GPL-2700T starting battery. My second battery is outboard of the port dinette under the seat.
I two have solar panels, each 850 watt units.
I'm sorry the pictures are too large for the website. If you want to see them, contact me and I'll e-mail them to you.
Lou
Lou Bruska
Sojourn
1985 C-36 Mk-I TR #495
Eldean Shipyard
Lake Macatawa (Holland, MI) Lake Michigan
Rallyback@comcast.net
Lou,
On your boat, for the three batteries in the seat forward of the nav station, how much did you or the PO have to modify that location to fit 2x31s and 1x24?
I have no idea what the original layout of that spot is (mine is effectively a fiberglass square crate/box on a platform without a lid), but I assume it's the OEM box tabbed in since I don't see any screw heads or bolts. It has places for the 2x24s inside plastic battery boxes, and not much else usable space at the moment, unless I break that box apart and remodel the space. I'm starting to look at how I can use this area more effectively, while getting a larger house bank and keeping the start battery in that location, too. I'm looking for options that allow me to do that without cutting into the gel coat of the seat the life I'd seen in some of the 6v modifications that people did. Denis's pictures show that the later boats certainly have better access to that area than the MkI does.
If anyone else has thoughts on this or wants to share what they did I'm all ears.
J. W. Bell
S/V <currently unnamed>
1985 MkI TR #462 M25
MKE, WI
Did how much you used the nav table change at all when you put the device there?
Denis - Is your unit roughly ~8 1/4" deep?
Lou - I can't say I've spent much time under there to know what is what. How much effort was it to mount/revise on the outside wall? ('d love to see the photos I'll DM you)
J. W. Bell
S/V <currently unnamed>
1985 MkI TR #462 M25
MKE, WI
The nav station is handy for storage of small important stuff but I never used it as a nav desk. Nice as the swinging chair was it took up too much room so I removed it. Eventually I plan on using the remaining space for a galley storage cabinet.
The Multiplus is 8 inches deep and a heavy beast too but it makes life on the boat comfortable and convenient.
Denis
Brazen Article #1925
2001 Catalina 36 MKII
Gentlemen,
Sorry for not commenting earlier. When I bought the boat, it had two batteries in place. I initially replace them in kind with two series 31's. They were mounted lengthwise athwart ship. When I went to 3 batteries I removed the wood blocks (1" X 2" strips) acting as base containment for the batteries and added a new base. I used left over 1/2" marine ply wood screwed into the old base and them glassed over it to waterproof it. The new base is wider both lengthwise (fore and aft) and wider athwart ship. I reinstalled new strips fore and aft and battery tie down cable on the fore and aft end. On top of the outboard strip I mounted terminal strips for the battery cables. Between each battery to act as insulation used some left over Star Board Plastic Marine Lumber. On the battery terminals I use the red and black battery terminal covers.
Hope this helps.
Lou Bruska
Sojourn
1985 C-36 Mk-I TR #495
Eldean Shipyard
Lake Macatawa (Holland, MI) Lake Michigan
Rallyback@comcast.net